add contributros

[xyb]

Closes #20

[codecov-commenter]

Codecov Report

Merging #23 (6759050) into main (6d06150) will increase coverage by 8.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   78.00%   86.28%   +8.28%     
==========================================
  Files           6        6              
  Lines         700      700              
==========================================
+ Hits          546      604      +58     
+ Misses        154       96      -58     

Impacted Files	Coverage Δ
juicefs/io.py	87.14% <0.00%> (+20.71%)	⬆️

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